U.S. patent number 7,599,190 [Application Number 10/502,117] was granted by the patent office on 2009-10-06 for high-frequency module, and method of producing same.
This patent grant is currently assigned to Sony Corporation. Invention is credited to Akihiko Okubora.
United States Patent |
7,599,190 |
Okubora |
October 6, 2009 |
High-frequency module, and method of producing same
Abstract
A high-frequency module having a communication function is
provided which includes a base substrate block (2) formed from
organic substrates (11, 12), the organic substrate (11) having
wiring layers (14, 15) formed on main sides, respectively, thereof
while the organic substrate (12) has wiring layers (16, 17) formed
on main sides, respectively, thereof, the base substrate block (2)
having a buildup surface formed by flattening an uppermost layer,
and an elements block (3) formed from organic insulative layers
(26, 28) formed on the buildup surface of the base substrate block
(2) and in which a plurality of conductive parts (19, 20, 32)
forming passive elements and distributed parameter elements, which
transmit a high-frequency signal, are formed along with wiring
layers (27, 29). The conductive parts (19, 20, 32) in the elements
block (3) are formed correspondingly to portions of the organic
substrate (11) in the base substrate block (2) where no woven glass
fabric is laid.
Inventors: |
Okubora; Akihiko (Kanagawa,
JP) |
Assignee: |
Sony Corporation (Tokyo,
JP)
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Family
ID: |
27606174 |
Appl.
No.: |
10/502,117 |
Filed: |
January 24, 2003 |
PCT
Filed: |
January 24, 2003 |
PCT No.: |
PCT/JP03/00684 |
371(c)(1),(2),(4) Date: |
July 21, 2004 |
PCT
Pub. No.: |
WO03/063238 |
PCT
Pub. Date: |
July 31, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050146403 A1 |
Jul 7, 2005 |
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Foreign Application Priority Data
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Jan 25, 2002 [JP] |
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2002-017620 |
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Current U.S.
Class: |
361/760; 361/795;
361/765; 361/763 |
Current CPC
Class: |
H05K
3/4602 (20130101); H05K 1/16 (20130101); H01L
23/49833 (20130101); H01L 23/66 (20130101); H05K
3/4688 (20130101); H01L 2924/19107 (20130101); H05K
2203/1581 (20130101); H05K 2201/0352 (20130101); H05K
1/024 (20130101); H05K 1/162 (20130101); H01L
2224/48091 (20130101); H01L 2924/181 (20130101); H01L
2924/19105 (20130101); H01L 2924/14 (20130101); H01L
2924/01078 (20130101); H01L 2224/16237 (20130101); H01L
2924/20752 (20130101); H01L 24/45 (20130101); H01L
2924/09701 (20130101); H01L 2924/01014 (20130101); H01L
2924/01028 (20130101); H01L 2924/12042 (20130101); H01L
2224/45015 (20130101); H01L 2924/01079 (20130101); H01L
2924/30107 (20130101); H01L 2224/16225 (20130101); H01L
23/145 (20130101); H05K 1/0366 (20130101); H01L
2924/01013 (20130101); H05K 1/167 (20130101); H01L
2924/3025 (20130101); H05K 2201/029 (20130101); H01L
24/48 (20130101); H01L 2924/00014 (20130101); H01L
2224/48091 (20130101); H01L 2924/00014 (20130101); H01L
2224/45015 (20130101); H01L 2924/20752 (20130101); H01L
2924/12042 (20130101); H01L 2924/00 (20130101); H01L
2924/14 (20130101); H01L 2924/00 (20130101); H01L
2924/181 (20130101); H01L 2924/00012 (20130101); H01L
2924/00014 (20130101); H01L 2224/45015 (20130101); H01L
2924/207 (20130101); H01L 2924/00014 (20130101); H01L
2224/45099 (20130101) |
Current International
Class: |
H05K
7/02 (20060101); H05K 7/06 (20060101); H05K
7/08 (20060101); H05K 7/10 (20060101) |
Field of
Search: |
;361/763-766,782-783,792-795 ;333/33-35 ;257/685-687 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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03-166930 |
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Jul 1991 |
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JP |
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05-338034 |
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Dec 1993 |
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JP |
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09-260797 |
|
Oct 1997 |
|
JP |
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10-117048 |
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May 1998 |
|
JP |
|
2000-044776 |
|
Feb 2000 |
|
JP |
|
2000-265039 |
|
Sep 2000 |
|
JP |
|
2000-340904 |
|
Dec 2000 |
|
JP |
|
Primary Examiner: Dinh; Tuan T
Attorney, Agent or Firm: Depke; Robert J. Rockey, Depke
& Lyons, LLC
Claims
The invention claimed is:
1. A high-frequency module comprising: a first organic substrate
having no glass fibers with conductive portions formed on top and
bottom surfaces of the first organic substrate; a second organic
substrate having conductive portions formed on top and bottom
surfaces of the second organic substrate; a prepreg layer having no
glass fibers exclusively located between the first and second
organic substrates; an insulating layer formed over the conductive
portions formed at the top surface of the first organic substrate
and wherein high frequency circuit components are formed over the
insulating layer and there is no conductive portion on either the
top or bottom surfaces of the first organic substrate located
perpendicularly below high frequency circuit components that are
formed over the insulating layer; a high frequency integrated
circuit located above the high frequency components and wherein
conductors transmit electrical signals through the first and second
organic substrates and the prepreg layer to conductive pads located
beneath the second organic substrate.
2. The high-frequency module according to claim 1, wherein said
first organic substrate is formed from either liquid crystal
polymer or liquid crystal polymer having a ceramic powder dispersed
therein.
3. The high-frequency module according to claim 1, wherein said
first organic substrate is formed from either benzocyclobutene or
benzocyclobutene having a ceramic powder dispersed therein.
4. The high-frequency module according to claim 1, wherein said
first organic substrate is formed from either polynorbornen or
polynorbornen having a ceramic powder dispersed therein.
5. The high-frequency module according to claim 1, wherein said
first organic substrate is formed from either polyphenylether or
polyphenylether having a ceramic powder dispersed therein.
6. The high-frequency module according to claim 1, wherein said
first organic substrate is formed from either
polytetrafluoroethylene or polytetrafluoroethylene having a ceramic
powder dispersed therein.
7. The high-frequency module according to claim 1, wherein said
first organic substrate is formed from either bismaleimide-triazine
or bismaleimide-triazine having a ceramic powder dispersed
therein.
8. The high-frequency module according to claim 1, wherein said
first organic substrate is formed from polyimide having a ceramic
powder dispersed therein.
9. The high frequency module of claim 1, wherein the second organic
substrate has glass fibers located therein.
10. The high frequency module of claim 1, wherein the second
organic substrate has no glass fibers located therein.
11. A method of manufacturing a high-frequency module comprising:
providing a first organic substrate having no glass fibers with
conductive portions formed on top and bottom surfaces of the first
organic substrate; providing a second organic substrate having
conductive portions formed on top and bottom surfaces of the second
organic substrate; forming a prepreg layer having no glass fibers
exclusively located between the first and second organic substrates
having the conductive portions formed thereon; forming an
insulating layer over the conductive portions formed at the top
surface of the first organic substrate and forming high frequency
circuit components over the insulating layer and wherein there is
no conductive portion on either the top or bottom surfaces of the
first organic substrate located perpendicularly below high
frequency circuit components that are formed over the insulating
layer; providing a high frequency integrated circuit above the high
frequency components and wherein conductors transmit electrical
signals through the first and second organic substrates and the
prepreg layer to conductive pads located beneath the second organic
substrate.
Description
TECHNICAL FIELD
The present invention relates to a high-frequency module having
functions of information communication and storage and which is to
be installed fixedly or removably as an ultra-small communication
module in an electronic device such as a personal computer,
personal digital assistant, mobile phone or an audio device to
provide an ultra-compact communication module, and a method of
producing the high-frequency module.
This application claims the priority of the Japanese Patent
Application No. 2002-017620 filed on Jan. 25, 2002, the entirety of
which is incorporated by reference herein.
BACKGROUND ART
Conventionally, audio or video information is digitized for easy
treatment in a personal computer, various mobile electronic devices
or the like. Namely, digital data can easily be recorded,
reproduced or transmitted without being deteriorated in quality.
Such digital audio or video information can have its frequency band
compressed with the audio and video codec techniques for easier and
more efficient distribution to a variety of communication terminals
via digital communication and broadcasting. For example, audio and
video data (AV data) can be received by a mobile phone out of
doors.
Recently, transmission/reception systems for such digital
information are practically used in various manners since there
have been proposed network systems suitable for outdoor use as well
as for use in a small-scale area. As such network systems, there
have been proposed, in addition to a week radio-wave system using a
frequency band of 400 MHz and personal handy-phone system (PHS)
using a frequency band of 1.9 GHz, various types of next-generation
radio communication systems including a radio LAN system using a
frequency band of 2.45 GHz and small-scale radio communication
system called "Bluetooth", both proposed in IEEE 802.11b, and a
narrow-band radio communication system using a frequency band of 5
GHz proposed in IEEE 802.11a. With the effective use of such
various radio communication system and also various types of
communication terminals, the digital information
transmission/reception systems can transfer and receive various
kinds of data by various types of communication terminals in
various places, for example, in doors, out of doors or the like,
access a communication network such as the Internet, and transmit
and make data transmission and reception to and from the
communication network. However, the above data communications can
be done easily, not via any repeater or the like.
For the digital information transmission/reception systems,
however, the communication terminal having the above communication
functions should essentially be compact and lightweight, and
portable. Since the communication terminal has to modulate and
demodulate analog high-frequency signals in a
transmission/reception block thereof, so it generally includes a
high-frequency transmission/reception circuit of a superheterodyne
type designed to convert the signal frequency into an intermediate
frequency once for transmission or reception.
The high-frequency transmission/reception circuit includes an
antenna block having an antenna and a select switch and which
receives or transmits information signals, and a
transmission/reception selector which makes a selection between
transmission and reception modes of operation. The high-frequency
transmission/reception circuit also includes a reception circuit
block composed of a frequency convert circuit, demodulation
circuit, etc. The high-frequency transmission/reception circuit
further includes a transmission circuit block composed of a power
amplifier, drive amplifier, modulation circuit, etc. The
high-frequency transmission/reception circuit also includes a
reference frequency generation circuit block which supplies a
reference frequency to the reception and transmission circuit
blocks.
The above-mentioned high-frequency transmission/reception circuit
is composed of many parts including large functional components
such as various filters interposed between stages, local oscillator
(VCO), surface acoustic wave (SAW) filter and the like, and passive
components such as an inductor, capacitor, resistor and the like
provided peculiarly to high-frequency analog circuits like a
matching circuit, bias circuit, etc. In the high-frequency
transmission/reception circuit, each of the circuit blocks is
implemented in IC-chip form. However, since each of the filters
interposed between the stages cannot be assembled in any IC, the
matching circuit has to be provided as an external device for the
high-frequency transmission/reception circuit. Therefore, the
high-frequency transmission/reception circuit as a whole is so
large that the communication terminal cannot be designed compact
and lightweight.
On the other hand, some communication terminals use a direct
conversion-type high-frequency transmission/reception circuit which
transmits and receives information signals without conversion of
the signal frequency into an intermediate frequency. In this
high-frequency transmission/reception circuit, information signals
received by the antenna block are supplied through the
transmission/reception selector to the demodulation circuit where
they will undergo a direct baseband processing. In the
high-frequency transmission/reception circuit, information signals
generated by a source have the frequency thereof not converted once
by the modulation circuit into any intermediate frequency but
modulated directly to a predetermined frequency band, and sent from
the antenna block via the amplifier and transmission/reception
selector.
Since the above high-frequency transmission/reception circuit is
constructed to transmit and receive information signals with the
direction modulation of the signal frequency but without conversion
of the signal frequency into any intermediate frequency, it can be
composed of a reduced number of parts such as the filter etc. so
simply as to have a generally one-chip construction. Also, in the
high-frequency transmission/reception circuit of the direct
conversion type, something has to be done about the filter or
matching circuit provided in the downstream stage. In the
high-frequency transmission/reception circuit, since signals are
amplified once in the high-frequency stage, so it is difficult to
make a sufficient gain. Therefore, it is necessary to make
amplification of the signals in the baseband processing block as
well. Therefore, a DC offset cancel circuit and an extra lowpass
filter have to be provided in the high-frequency
transmission/reception circuit, which will lead to a larger total
power consumption.
The conventional high-frequency transmission/reception circuit,
whether of the aforementioned superheterodyne type or of the direct
conversion type, does not meet the requirements for the compact and
lightweight design of the communication terminals. On this account,
various approaches have been made to design a more compact and
lightweight high-frequency transmission/reception circuit by
designing a simple-construction high-frequency
transmission/reception module with the Si-CMOS technique, for
example. In a typical example of such approaches, the
high-frequency module is built in a one-chip form by forming
passive elements each having a good performance on an Si substrate
while forming a filter circuit and resonator in an LSI and
integrating an logic LSI for the baseband processing circuit. Since
the Si substrate is electrically conductive, however, it is
difficult to form an inductor and capacitor each having a high Q
value on the main side of the Si substrate. In this case, such
approaches essentially depend upon how higher-performance passive
elements are formed on the Si substrate.
FIGS. 1A and 1B show together a conventional high-frequency module.
The high-frequency module is generally indicated with a reference
100. It includes a silicon substrate 101, SiO.sub.2 insulative
layer 102, first wiring layer 105, second wiring layer 106 and an
inductor 107. The assembly of the silicon substrate 101 and
SiO.sub.2 insulative layer 102 has formed therein a large concavity
104 which defines a place (indicated at a reference 103) where the
inductor 107 is to be formed. The first wiring layer 105 is formed
in the concavity 104. The second wiring layer 106 is formed on the
top of the silicon layer 101 and the inductor 107 itself is
provided over the concavity 104. Since the inductor 107 faces the
concavity 104 and is supported by the second wiring layer 106 in
air over the concavity 103, so its electrical interference with the
circuit inside via the silicon substrate 101 is smaller, and thus
the high-frequency module 100 has an improved performance. However,
the inductor 107 included in this high-frequency module 100 is
formed through many difficult processes and with an increased
manufacturing cost.
FIG. 2 shows a conventional silicon substrate. As shown, the
silicon substrate, generally indicated with a reference 110,
includes a silicon substrate 111, SiO.sub.2 layer 112 formed on the
silicon substrate 111, and a passive element forming layer 113
formed on the SiO2 layer 111 by the photolithography. The
high-frequency module 110 has passive elements such as an inductor,
capacitor or resistor formed in multiple layers, each along with a
wiring element, in the passive element forming layer 113 with the
thin and thick film technologies, which will not be described in
detail herein. In the high-frequency module 110, the passive
element forming layer 113 has viaholes 114 formed appropriately
therethrough to provide an interlayer connection and a terminal 115
formed on the surface layer thereof. A chip 116 such as a
high-frequency IC, LSI or the like is mounted on the high-frequency
module 110 on contact with the terminal 115 by the flip chip
bonding or the like to form a high-frequency circuit.
Such a high-frequency module 110 is mounted on an interposer
circuit board or the like having a base-band processing circuit and
the like formed thereon to make an isolation between the passive
element forming layer and base-band processing circuit by means of
the silicon layer 111, thereby permitting to suppress an electric
interference between the passive element forming layer and
base-band processing circuit. Since the silicon layer 111 is
electrically conductive, the high-frequency module 110 can
effectively function when a high-precision passive element is
formed in the passive element forming layer 113. On the other hand,
however, the silicon layer 111 being electrically conductive will
inhibit each of passive elements from a having good high-frequency
performance.
FIG. 3 shows another conventional high-frequency module. The
high-frequency module, generally indicated with a reference 120,
uses a substrate 121 not electrically conductive such as a glass
substrate or ceramic substrate to solve the problems of the
aforementioned silicon substrate 111. As shown, this high-frequency
module 120 includes a substrate 121 and a passive element forming
layer 122 formed on the substrate 121 by photolithography.
Similarly to the aforementioned conventional high-frequency module
110, the high-frequency module 120 has passive elements such as an
inductor, capacitor or resistor formed in multiple layers, along
with a wiring element, in the passive element forming layer 122
with the thin and thick film technologies, which will not be
described in detail herein. In the high-frequency module 120, the
passive element forming layer 122 has a viahole 123 formed
appropriately therethrough for an interlayer connection, and a
terminal 124 formed on the surface layer thereof. A high-frequency
IC 125, chip-shaped part 126 and the like are mounted on the
high-frequency module 120 with the terminal 124 laid between them
by the flip chip bonding or the like to form a high-frequency
circuit.
In the high-frequency module 120 shown in FIG. 3, since use of the
substrate 121 not electrically conductive permits to suppress the
capacitive coupling between the substrate 121 itself and passive
element forming layer 122, a passive element having a good
high-frequency performance can be formed in the passive element
forming layer 122. In case the high-frequency module 120 is formed
from a glass substrate, however, it is difficult because of the
characteristic of the glass substrate to form, on the substrate 121
itself, terminals by which the high-frequency module 120 is
connected to an interposer substrate 127, for example, when it is
mounted on the latter. On this account, in the high-frequency
module 120, a terminal pattern 128 is appropriately formed on the
surface of the passive element forming layer 122, and the terminal
pattern 128 and a terminal pattern 129 appropriately formed at the
interposer substrate 127 are connected to each other by a wire 130
with the wire bonding technique or the like, as shown in FIG. 4. It
should be noted that the interposer substrate 127 has appropriately
formed on the bottom thereof an input/output terminal 131 connected
to the terminal pattern 128 through viaholes (not shown).
The above high-frequency module 120 is not advantageous in that the
terminal patterns 128 and 129 have to be formed and connected by
wire bonding to each other, which will increase the cost of
manufacturing and make it difficult to attain a more compact module
design. It should be noted that the high-frequency module 120 is
packaged with the terminal patterns 128 and 129 or the wire 130
being sealed along with high-frequency IC 125 and chip-shaped part
126 in an insulative resin 132.
On the other hand, in case the high-frequency module 120 is formed
from a ceramic substrate, it functions as a package board on no
contact with any mother board because a base ceramic substrate can
be formed in multiple layers. Since the ceramic substrate is formed
from sintered ceramic particles, however, it will have, on a
surface thereof where the passive element forming layer 122 is
formed, a roughness as large as the ceramic particle size of about
2 to 10 .mu.m. Therefore, to form high-precision passive elements
in the high-frequency module 120, the ceramic layer surface has to
be flattened by polishing before forming the passive element
forming layer 122. Also, since the ceramic substrate has a
relatively high specific inductive capacity (8 to 10 in case the
ceramic substrate is of alumina, and 5 to 6 in case it is of glass
ceramic) while it is low in loss, so the high-frequency module 120
will incur interference between multiple layers of wiring, be lower
in reliability and less immune to noises.
To solve the problems of the aforementioned conventional
high-frequency modules, the Applicant of the present invention
proposed another high-frequency module as shown in FIG. 5. The
high-frequency module, generally indicated with a reference 140,
includes a base substrate block 141 and a block in which elements
are formed (will be referred to as "elements block" hereunder) 142
stacked on the base substrate block 141. The base substrate block
141 is formed from first and second organic substrates 143 and 144
each low in loss because of their low specific inductive capacity
and dielectric dissipation factor (Tan .delta.), and the first and
second organic substrates 143 and 144 are bonded integrally to each
other with a prepreg 145.
The first and second organic substrates 143 and 144 are formed from
a material having the aforementioned characteristics, selected from
among organic materials including liquid crystal polymer,
benzocyclobutene, polymide, polynorbornen, polyphenylether,
polytetrafluoroethylene, bismaleimide-triazine (BT-resin) and any
one of these resins having ceramic powder dispersed therein, with
the material being integrated with woven glass fabrics 146a and
146b each as a core to assure an improved bending strength, rupture
strength, etc.
The base substrate block 141 has a wiring layer formed, with the
printed-circuit board technique, on the main side, top or bottom,
of each of the first and second organic substrates 143 and 144 to
form first to fourth wiring layers 147 to 150. Of the base
substrate block 141, the first to fourth wiring layers 147 to 150
are interlayer-connected to each other through viaholes 151
appropriately formed through the layers 147 to 150. The first and
second wiring layers 147 and 148 are formed on the top and bottom
main sides, respectively, of the first organic substrate 143, while
the third and fourth wiring layers 149 and 150 are formed on the
top and bottom sides, respectively, of the second organic substrate
144. The high-frequency module 140 has formed inside the base
substrate block 141 thereof line patterns 152a and 152b each formed
from a distributed parameter circuit including a resonator, filter,
etc. or a power circuit, bias circuit, etc. which will not be
described in detail.
The high-frequency module 140 shown in FIG. 5 has a passive element
153, inductor 154, passive element 155 or the like formed in the
elements block 142 with the thin film technology. In the
high-frequency module 140, a high-frequency IC 156 is mounted on
the surface of the element forming layer 142 by the flip chip
bonding. To efficiently form the line patterns 152a and 152b, power
circuit or bias circuit formed in the base substrate block 141 and
the passive elements 153 to 155 formed in the element forming layer
142 as above and avoid interference between the elements, the
high-frequency module 140 has the first and third wiring layers 147
and 149 formed each as a grounding layer.
Note that the high-frequency module 140 shown in FIG. 5 is packaged
with the wiring pattern formed on the surface of the elements block
142 being covered with a protective layer 157 while the
high-frequency module 140 and a high-frequency IC 156 are wholly
covered with an insulative resin layer (not shown). The
high-frequency module 140 has a plurality of terminal blocks 158
formed in the fourth wiring layer 150, and mounted on an interposer
(not shown) with the terminal blocks 158 being positioned between
them.
The high-frequency module 140 shown in FIG. 5 is characterized in
that since the first and second organic substrates 143 and 144 are
formed from a relatively low-cost material, the module 140 itself
can be produced with a reduced cost and that the desired first to
fourth wiring layers 147 to 150 can be formed more easily with the
printed-circuit board technique. By flattening the surface of the
base substrate block 141 by polishing, for example, the
high-frequency module 140 can have the passive elements 153 to 155
formed in the element forming layer 142 with a high precision.
Also, since the base substrate block 141 and element forming layer
142 are electrically isolated from each other to improve the
performance and assure a power circuit etc. having a sufficiently
large area, so the high-frequency module 140 can be supplied with a
high-regulation power.
Also, in the high-frequency module 140 shown in FIG. 5, the passive
elements 153 to 155 formed in the element forming layer 142 are
influenced by the ground pattern formed on the first wiring layer
147 at the base substrate block 141. In the high-frequency module
140, the inductor 154, for example, develops a capacitance between
itself and the ground pattern to have a reduced self-resonant
frequency and quality factor Q. In the high-frequency module 140,
the passive elements 153 and 155 also vary or becomes worse in
performance.
To solve the problems of the aforementioned conventional
high-frequency module 140, there has been proposed another
high-frequency module as shown in FIG. 6. The high-frequency
module, generally indicated with a reference 160, has pattern
openings 161a and 161b formed in the ground pattern on the first
wiring layer 147 opposite to the passive elements 153 to 155 at the
element forming layer 142. It should be noted that since the
components of the high-frequency module 160 in FIG. 6 are the same
as those in the high-frequency module 140 shown in FIG. 5, so they
are indicated with the same references as those in FIG. 5 and will
not be described in detail any longer. Thus, in the high-frequency
module 160 shown in FIG. 6, the passive elements 153 to 155 will be
influenced by the third wiring layer 149 via the organic substrate
layer of the first organic substrate 143 and the prepreg 145, but
they will be improved in performance.
In the high-frequency module 140 in FIG. 5 and the one 160 in FIG.
6, each of the organic materials of the first and second organic
substrates 143 and 144 is a substrate material formed by
integrating a woven glass fabric with each of the first and second
organic substrates 143 and 144. Such a substrate material is formed
by continuously supplying a woven glass fabric, generally rolled in
the form of a roll, into a bath filled with an emulsified organic
material, thus saturating the woven glass fabric with the organic
material, adjusting the thickness of the organic material-saturated
woven glass fabric, drying the woven glass fiber, and make some
other process of the woven glass fabric to a desired thickness.
Then, the first and second organic substrates 143 and 144 are
formed by applying an adhesive to the top or bottom main side of
the substrate material as a core, bonding a rolled copper foil
having the surface thereof roughened to the substrate material and
cutting the latter to a predetermined size.
In the high-frequency module 160 in FIG. 6, since each of the
organic substrates is larger in specific inductive capacity than
the woven glass fabric, the line pattern 152 of the distributed
parameter circuit formed on the base substrate block 141 is
influenced in both conductor loss and inductive loss by the woven
glass fabric in the aforementioned first and second organic
substrates 143 and 144, and thus has the performance thereof
degraded. Also, in the high-frequency module 160 in FIG. 6, in case
the glass fibers are woven with a large pitch, the line pattern 152
will be formed over a portion where the glass fibers are laid and a
portion where no glass fibers exist are laid. In the high-frequency
module 160 in FIG. 6, the effective specific inductive capacity and
dielectric dissipation factor (Tan .delta.) "vary" in the first and
second organic substrates 143 and 144 depending upon whether or not
the glass fibers are laid. The "variation" of the effective
specific inductive capacity is found large where the glass fibers
are laid thick, and small where the glass fibers are laid thin.
Namely, the effective specific inductive capacity varies
periodically (with the pitch of the glass fibers) in a range of a
difference between the maximum and minimum values.
The high-frequency module 160 shown in FIG. 6 is lower in
reliability and yield in some cases because of the degraded
performance, larger "variation" and difficult reproducibility of
the line pattern 152. Thus, the high-frequency module 160 will be
higher in cost because it has to be adjusted after produced. Also,
in case the high-frequency module 160 has other lines and various
passive elements formed in the base substrate block 141 thereof
with the thin film technology in addition to the line pattern 152,
the same problems will possibly take place due to increases or
"variations" of effective specific inductive capacity and
dielectric dissipation factor (Tan .delta.) under the influence of
the glass fibers used to form the organic substrates.
DISCLOSURE OF THE INVENTION
Accordingly, the present invention has an object to overcome the
above-mentioned drawbacks of the related art by providing a novel
high-frequency module and a novel method of producing the
high-frequency module.
The present invention has another object to provide a
high-frequency module improved in performance, precision and
reliability through reduction of the degradation and variation of
each conductive part, caused by the glass fibers as the substrate
material, and a method of producing the high-frequency module.
The above object can be attained by providing a high-frequency
module including, according to the present invention, a wiring
pattern formed in an organic insulative layer and a plurality of
conductive parts forming passive elements and distributed parameter
elements, which transmit a high-frequency signal. In the
high-frequency module, each of the conductive parts is formed
correspondingly to an area of the organic insulative layer where no
woven glass fabric is laid.
In the above high-frequency module according to the present
invention, since each of the conductive parts is formed
correspondingly to the area where no woven glass fabric is laid,
the effective specific inductive capacity and dielectric
dissipation factor (Tan .delta.) are kept from increasing or
"varying" and the performance is thus improved.
Also, the above object can be attained by providing a
high-frequency module including, according to the present
invention, a base substrate block having formed on a main side of
an organic substrate a plurality of wiring layers each including an
organic insulative layer and a wiring pattern and having at least
the uppermost one of the wiring layers layer flattened to form a
buildup surface; and an elements block having formed in the organic
insulative layer formed on the main side of the buildup surface of
the base substrate block a wiring pattern and a plurality of
conductive parts forming passive elements and distributed parameter
elements, which transmit a high-frequency signal. In the
high-frequency module, each of the conductive parts of the elements
block is formed correspondingly to an area of the organic
insulative layer where no woven glass fabric is laid.
The above high-frequency module according to the present invention
can be produced with a reduced cost since the organic substrate is
available at a relatively low price, and the conductive parts
forming the passive elements and distributed parameter elements can
be formed with an improved precision since the elements block is
formed on the flat buildup surface of the base substrate block. In
the high-frequency module according to the present invention, since
each of the conductive parts is formed correspondingly to an area
where no woven glass fabric is laid, the effective specific
inductive capacity and dielectric dissipation factor (Tan .delta.)
can be kept from increasing or "varying" and thus the performance
and reliability can be improved.
Also, the above object can be attained by providing a method of
producing a high-frequency module includes, according to the
present invention, steps of forming a base substrate block and an
elements block. The base substrate block forming step further
includes steps of forming, on a main side of an organic substrate,
a plurality of wiring layers each including an organic insulative
layer and a predetermined wiring pattern; and forming a buildup
surface by flattening at the uppermost one of the wiring layers.
The elements block forming step further includes a step of forming,
in the organic insulative layer formed on the buildup surface of
the base substrate block, a wiring pattern and a plurality of
conductive parts forming passive elements and distributed parameter
elements, which transmit a high-frequency signal. In this method of
producing a high-frequency module, each of the conductive parts of
the elements block is formed correspondingly to an area of the
organic substrate where no woven glass fabric is laid.
The above method of producing a high-frequency module according to
the present invention permits to produce a high-frequency module
with a reduced cost since the organic substrate is available at a
relatively low price, and the conductive parts forming the passive
elements and distributed parameter elements can be formed with an
improved precision since the elements block is formed on the flat
buildup surface of the base substrate block. The method of
producing a high-frequency module according to the present
invention permits to keep the effective specific inductive capacity
and dielectric dissipation factor (Tan .delta.) from increasing or
"varying" and thus improve the performance and reliability of the
high-frequency module since each of the conductive parts is formed
correspondingly to an area where no woven glass fabric is laid.
These objects and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description of the best mode for carrying out the present
invention when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B show together an inductor provided in the
conventional high-frequency module, in which FIG. 1A is a
perspective view of the inductor and FIG. 1B is a sectional view of
the inductor.
FIG. 2 is an axial sectional view of the substantial part of the
conventional high-frequency module using a silicon substrate.
FIG. 3 is also an axial sectional view of the substantial part of
the conventional high-frequency module using a glass substrate.
FIG. 4 is an axial sectional view of the substantial part of the
conventional high-frequency module used in an interposer.
FIG. 5 is an axial sectional view of a high-frequency module in
which a high-frequency elements block is formed from a multilayer
organic substrate as a base by stacking.
FIG. 6 is an axial sectional view of a high-frequency module having
formed in a base substrate block a pattern opening correspondingly
to a passive element formed in a high-frequency forming block.
FIG. 7 is an axial sectional view of the substantial part of a
high-frequency module according to the present invention.
FIG. 8 is also an axial sectional view of the substantial part of
an organic substrate used in producing the high-frequency module
according to the present invention.
FIG. 9 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing
the construction of first and second organic substrates.
FIG. 10 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing
the construction of the first and second organic substrates and a
prepreg.
FIG. 11 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing a
base substrate block including the first and second organic
substrates formed integrally with each other with the prepreg being
disposed between them.
FIG. 12 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing a
first dielectric insulative layer formed on a first wiring layer of
the base substrate to form a first layer of the elements block.
FIG. 13 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing a
fifth wiring layer formed on the first dielectric insulative layer
and then anodized.
FIG. 14 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing
capacitor element electrodes formed on the fifth wiring layer.
FIG. 15 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing a
second dielectric insulative layer formed on the fifth wiring
layer.
FIG. 16 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing a
sixth wiring layer formed on the second dielectric insulative
layer.
FIG. 17 is an axial sectional view of the substantial part of the
high-frequency module according to the present invention, showing
an insulative protective layer formed on the sixth wiring layer to
form the elements block.
FIG. 18 is an axial sectional view of the substantial part of a
second embodiment of the high-frequency module according to the
present invention, in which the second organic substrate in the
lower portion is formed from an organic substrate including a woven
glass fabric as a core.
FIG. 19 is an axial sectional view of the substantial part of a
third embodiment of the high-frequency module according to the
present invention, in which a strip-line structure of lines is
formed on organic substrates without the woven glass fabric which
is laid between the organic substrates including the woven glass
fabric as a core.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described concerning embodiments
thereof with reference to the accompanying drawings.
The high-frequency module according to the present invention has an
information communication function, information storage function,
etc. and it is to be used as an ultra-small communication module or
the like fixedly installed or removably installed as an option in
an electronic apparatus such as a personal computer, mobile phone,
portable digital assistant or a portable audio device. Especially,
the high-frequency module according to the present invention is
used in an appropriate small-scale radio communication system using
a carrier frequency band of 5 GHz, for example.
As shown in FIG. 7, the high-frequency module according to the
present invention, generally indicated with a reference 1, includes
a base substrate block 2 and an elements block 3 stacked on the
base substrate block 2 and having an appropriate wiring pattern 4
and lands 5 formed on the surface thereof. The high-frequency
module 1 includes an IC chip 6 having a peripheral circuit function
of a high-frequency transmission/reception circuit, electronic
parts, etc. (not shown) mounted thereon by the flip chip bonding
with the lands 5 laid between them. The wiring pattern 4 formed on
the surface of the elements block 3 is covered with an insulative
protective layer 7 of solder resist or the like, and the
high-frequency module 1 as a whole including the IC chip 6 is
covered with an insulative resin layer 8. That is, the
high-frequency module 1 is thus packaged. The high-frequency module
1 has multiple terminals 9 formed on the bottom of the base
substrate block 2, and is mounted on an interposer substrate 10
(will not be illustrated and described in detail) with the
terminals 9 laid between them.
In the high-frequency module 1 according to the present invention,
the base substrate block 2 has formed therein circuits such as a
power source, control system, etc. for the elements block 3, and
also the high-frequency module 1 is mounted at the base substrate
block 2 thereof on the interposer substrate 10. In the
high-frequency module 1, the base substrate block 2 and elements
block 3 are electrically isolated from each other to suppress the
electric interference between the base substrate block 2 and
elements block 3, thereby assuring an improved performance. Also,
in the high-frequency module 1, since the power source and ground,
each having a sufficient area are formed in the base substrate
block 2, so the power source can supply a power to the elements
block 3 with a high regulation.
The base substrate block 2 includes first and second organic
substrates 11 and 12 as will be described in detail later. The
first and second organic substrates 11 and 12 are bonded integrally
to each other with a prepreg 13. That is, the base substrate block
2 has first and second wiring layers 14 and 15 formed therein by
patterning the top and bottom main sides of the first organic
substrate 11 by photolithography and then removing unnecessary
copper foil portions by etching. Similarly, the base substrate
block 2 has a total of four layers including third and fourth
wiring layers 16 and 17 formed on the upper and lower main sides,
respectively, of the second organic substrate 12, in addition to
the first and second wiring layers 14 and 15, and the second and
first organic substrates 12 and 11 are bonded to each other with
the prepreg 13 laid between them. In the base substrate block 2,
the first to fourth wiring layers 14 to, 17 are
interlayer-connected to each other through via holes 18
appropriately formed.
In the base substrate block 2, the first and third wiring layers 14
and 16 form together a ground layer to shield the second wiring
layer 15. The first wiring layer 14 has pattern openings 21 and 22
formed therein in places opposite to a capacitor 19 and inductor
20, respectively, formed in the elements block 3 with the thin film
technology as will be described in detail later. The third wiring
layer 16 is formed as a so-called solid pattern having a copper
foil layer left over the first organic substrate 11. The second
wiring layer 15 includes resonator patterns 23a and 23b, for
example, formed from a distributed parameter circuit of a strip
line structure. The resonator patterns 23a and 23b have an electric
length of about .lamda./4 of the 5 GHz carrier frequency band, that
is, a length of about 6 mm, and are short-circuited at one end
thereof to the ground and open-circuited at the other end, which
will not be described in detail.
The fourth wiring layer 17 is covered with a protective layer 24 of
a solder resist or the like, and has openings formed in
predetermined places the protective layer 24 by photolithography or
the like. In the base substrate block 2, the terminal 9 of the
fourth wiring layer 17 exposed from each opening is coated with
Ni--Au by solderless plating, for example, to form an electrode 25,
and the high-frequency module 1 is mounted on the interposer
substrate 10 with the electrodes 25 being laid between them. The
base substrate block 2 has a buildup surface formed by flattening
the first wiring layer 14 at the first organic substrate 11 and
where the elements block 3 is formed by stacking, as will be
described in detail later.
The elements block 3 has two layer structures, one including a
first dielectric insulative layers 26 and fifth wiring layer 27
stacked on the buildup surface of the base substrate block 2, and
the other including a second dielectric insulative layer 28 and
sixth wiring layer 29 (wiring pattern 4). In the element forming
layer 3, the fifth wiring layer 27 is interlayer-connected to the
first wiring layer 14 through viaholes 30 appropriately formed in
the first dielectric insulative layer 26, and also the fifth and
sixth wiring layers 27 and 29 are interlayer-connected to each
other through viaholes 31 appropriately formed in the second
dielectric insulative layer 28. The fifth wiring layer 27 has the
capacitor 19 and a resistor 32 formed thereon with the thin film
technology. The sixth wiring layer 29 has the inductor 20 formed
thereon with the thin film technology, and the multiple lands 5
formed thereon.
According to the present invention, the high-frequency module 1 is
produced through a step of forming the base substrate block 2, and
a step of forming the elements block 3 on the base substrate block
2 by stacking.
The base substrate block forming step will be described with
reference to FIGS. 8 to 11.
First as shown in FIG. 8, in the base substrate block forming step,
an organic substrate material 33 is supplied to form the first and
second organic substrates 11 and 12. The organic substrate material
33 includes a core substrate 34, and copper foils 35 and 36 bonded
to the top and bottom main sides, respectively, of the core
substrate 34 as shown in FIG. 2.
The core substrate 34 is formed from an organic material low in
specific inductive capacity and dielectric dissipation factor (Tan
.delta.), that is, superior in high-frequency performance and
having a resistance against a temperature higher than 160.degree.
C. The core substrate 34 is thus formed from an organic material
selected from among liquid crystal polymer (LCP), benzocyclobutene
(BCB), polyimide, polynorbornen (PNB), polyphenylether (PPE),
polytetrafluoroethylene ("Teflon" as registered trademark),
bismaleimide-triazine (BT-resin) or any one of these organic
materials having an inorganic material such as ceramic powder or
the like dispersed therein.
The core substrate 34 is formed by any appropriate method of
molding any of the above-mentioned organic materials melted in an
appropriate solvent, for example, by blowing compressed air to the
mixture to swell it to have a predetermined shape or pouring the
mixture into a tray whose bore is shaped in a predetermined form
and inner surface is pre-applied with a release agent or the like
and solidifying it by cooling. The above organic substrate material
33 is formed by bonding copper foils 35 and 36 whose surfaces are
appropriately roughened to top and bottom main sides, respectively,
of the core substrate 34.
In the base substrate block forming step, through-holes are next
formed in appropriate positions through the organic substrate
material 33. They extend between the top and bottom main sides of
the latter. The through-holes are formed in the similar manner to
that normally adopted in the conventional multilayer substrate
forming step, for example, by forming a through-hole in a
predetermined position by a drill or laser, making a copper plating
on the wall of the through-hole thus formed to make the
through-hole wall electroconductive, embedding a paste in the
through-hole and making copper plating of the through-hole to lid
the latter. With a wiring pattern being formed on the top and
bottom main sides of the organic substrate material 33 by
photolithography and etching of the copper foils 35 and 36 to
remove other than necessary copper foil portions, the first and
second organic substrates 11 and 12 are formed as shown in FIG.
9.
The first organic substrate 11 has the first wiring layer 14 formed
from the copper foil layer on the first main side and the second
wiring layer 15 formed from the copper foil layer on the second
main side as shown in FIG. 9. The first wiring layer 14 forms a
ground layer and has the pattern openings 21 and 22 formed in a
portion thereof, as mentioned above. The second wiring layer 15 has
a control circuit etc. and strip line-structured resonator patterns
23a and 22b formed thereon as mentioned above. As shown in FIG. 3,
the second organic substrate 12 has the third wiring layer 16
formed from the copper foil layer on the first main side, and
fourth wiring layer 17 formed from the copper foil layer on the
second main side. The third wiring layer 15 has the copper foil
left over it to form a ground layer as mentioned above. The fourth
wiring layer 17 has formed thereon a wiring pattern which provides
a control circuit, power circuit, etc.
Next, in the base substrate block forming step, the aforementioned
first and second organic substrates 11 and 12 are integrated with
each other by the prepreg 13. For the purpose of this integration,
the first and second organic substrates 11 and 12 are positioned in
relation to each other, the prepreg 13 is interposed between the
main sides of the first and second organic substrates 11 and 12
opposite to each other as shown in FIG. 10, and the first and
second organic substrates 11 and 12 are subjected to a
hot-pressing, for example, to provide a base substrate
intermediate. Then, similarly to the above, in the base substrate
intermediate, there is formed through the first and second organic
substrates 11 and 12 a plurality of through-holes 18 that provide
appropriate connections among the first to fourth organic
substrates 14 to 17. Thus, the base substrate block 2 is formed as
shown in FIG. 11.
Note that the step of forming the base substrate block 2 is not
limited to the aforementioned one but the base substrate block 2
may be formed by one of the conventional printed-circuit board
techniques with which a insulative layer and wiring layer are
formed sequentially on a main side of a both-side copper clad
organic substrate, for example, as a base. In this case, the base
substrate block 2 is formed by forming a wiring layer on a
both-side copper clad organic substrate, then a dielectric
insulative layer on the wiring layer by applying a dielectric
insulative material to the wiring layer by spin coating, dipping or
the like, and predetermined pattern recesses corresponding to a
wiring pattern on the dielectric insulative layer with an
appropriate technique. The base substrate block 2 may have a
buildup surface formed thereon by forming a conductor layer over
the dielectric insulative layer by sputtering, for example, and
flattening the dielectric insulative layer and the conductor layer
in the pattern recesses by chemical polishing or the like. Also,
the base substrate block 2 may be formed by bonding a sheet-shaped
resin-lined copper foil to either side of a both-side copper clad
organic substrate having a copper foil provided on each side
thereof and patterned in a specific manner and patterning the
resin-lined copper foils. Further, the base substrate block 2 is
not limited in structure to the four-layer one but it may have more
layers formed therein as necessary.
The base substrate block 2 uses the first and second organic
substrates 11 and 12 or the prepreg 13, including no woven glass
fabric, as having been described above. The base substrate block 2
includes the aforementioned core substrate 34 formed from an
organic material. The core substrate 34 should preferably be formed
from an organic material whose softening point is higher than that
of the prepreg 13, especially, a thermoplastic resin such as PPE,
LCP or PNB. Since the core substrate 34 has no woven glass fabric
therein, the base substrate block 2 is low in productivity as
compared to the conventional organic substrate using, as a core
material, a woven glass fabric that can be formed continuously.
However, in the elements block 3 above the base substrate block 2
will have passive elements and wiring patterns formed therein with
the thin film technology employed in the semiconductor forming step
as will be described in detail later.
Therefore, the base substrate block 2 can surely be formed easily
through the manufacturing process and have an improved performance
since the core substrate 34 has not to be any large one and is
superior in flatness or uniformity owing to the techniques adopted
in the process. Thus the base substrate block 2 can be formed with
a higher precision and lower cost since the first to fourth wiring
layers 14 to 17 are formed from a relatively organic substrate with
the well-known printed-circuit board technique as having been
described above.
Of the base substrate block 2, the first organic substrate 11
having the first wiring layer 14 formed thereon has at least the
main side thereof is flattened. It should be noted that the
flattening may be such that the flattening may be done at the same
time for the fourth wiring layer 17 in order to equally finish the
top and bottom sides of the base substrate block 2 for inhibiting
any warping or the like from taking place. At the base substrate
block 2, the first wiring layer 14 is covered with an insulative
layer having a predetermined thickness, and the insulative layer is
surface-flattened by polishing with a polishing agent that is a
mixture of alumina and silica, for example, until the first wiring
layer 14 appears. The flattened surface of the base substrate block
2 provides a buildup surface on which the elements block 3 is to be
formed. Therefore, the base substrate block 2 can have the elements
block 3, which will be described in detail later, formed on the
buildup surface thereof by stacking with a high precision. It
should be noted that the flattening may also be done with any other
technique than the polishing, such as the reactive ion etching
(RIE) or plasma etching (PE), for example.
In the step of forming the base substrate block 2, an insulative
resin layer 37 forming the protective layer 24 is also formed on
the fourth wiring layer 17, as shown in FIG. 11, simultaneously
with the aforementioned insulative layer covering the first wiring
layer 14. The insulative resin layer 37 is polished simultaneously
with the polishing of the buildup surface, which is done when
polishing the first wiring layer 14. The insulative resin layer 37
is polished to such a limited extent that the fourth wiring layer
17 and each of the electrodes 25 will not be exposed, and so the
fourth wiring layer 17 will be protected against an etchant or a
mechanical or thermal load in the step of forming the elements
block 3, which will be described in detail later. It should be
noted that after the elements block 3 is formed, the insulative
resin layer 37 will be removed to expose each of the electrodes
25.
The base substrate block 2 formed through the aforementioned steps
is subjected to the elements block forming step will further be
subjected to the elements block forming step to have the element
forming layer 3 formed, by stacking, on the buildup surface having
been flattened by polishing.
Next, the elements block forming step will be illustrated and
described below with reference to FIGS. 12 to 17. In the step of
forming the elements block 3, a dielectric insulative material is
applied over the buildup surface of the base substrate block 2 to a
predetermined thickness to form the first dielectric insulative
layer 26 which forms a first one of the layers of the elements
block 3 as shown in FIG. 12.
As shown in FIG. 13, the first dielectric insulative layer 26 is
formed with an appropriate stacking technology capable of forming a
layer having a uniform thickness, such as spin coating, roll
coating or curtain coating. The first dielectric insulative layer
26 is also formed from an organic material excellent in
high-frequency performance, thermal resistance and chemical
resistance, such as BCB, PNB, LCP, polyimide or epoxy resin,
acrylic resin, polyolefin resin or the like. It should be noted
that although the buildup surface is formed by flattening the main
side of the base substrate block 2 in the step of forming the
high-frequency module 1, it may be formed by flattening the first
dielectric insulative layer 26 formed as above.
The first dielectric insulative layer 26 has formed therethrough
viaholes 30 through which there is exposed a part of the first
wiring layer 14 in the base substrate block 2. In case the first
dielectric insulative layer 26 is formed from a photosensitive
resin, for example, the viaholes 30 are formed by exposing the
first dielectric insulative layer 26 to light after
photolithography of the latter with a mast shaped as desired. Also,
in case the first dielectric insulative layer 26 is formed from a
non-photosensitive resin, for example, the viaholes 30 are formed
by dry etching such as a directional chemical etching using a
photoresist or metal film having a desired shape as a mask.
The first dielectric insulative layer 26 has a thin metal thin
formed over it by sputtering or the like to form the fifth wiring
layer 27 thereon. It should be noted that the first dielectric
insulative layer 26 may have a priming thin metal film of Cr, Ni,
Ti or the like, for example, preformed as a barrier layer thereon
by sputtering or the like and then have the thin metal layer formed
on the priming thin metal film to improve the adhesion. The thin
metal layer is formed from a combination of an Ni layer of about 50
nm in thickness and Cu layer of about 500 nm, or a combination of a
Ti layer of about 50 nm and Cu layer of about 500 nm, or the like.
The thin metal layer may be formed from Cu, Al, Pt, Au or the
like.
The thin metal layer should preferably be formed from a metal
selectable in etching the fifth wiring layer 27, as will be
descried in detail later. In case the fifth wiring layer 27 is
wet-etched with an etchant which is a mixture of nitric acid,
sulfuric acid and acetic acid, for example, the thin metal layer is
formed from Al, Pt or Au which is resistant against the etchant.
Among these metals, Al is most suitable because it can easily be
patterned. It should be noted that the thin metal layer is formed
on the inner wall of each viahole 30.
The thin metal layer is subjected to photolithography using a mask
having a desired shape and then etched to have formed thereon the
fifth wiring layer 27 having an under-electrode 19a on which the
capacitor 19 is provided and seat-electrodes 32a and 32b on which
the resistor 32 is provided as shown in FIG. 13. The fifth wiring
layer 27 has formed with the lift-off technique in place on the
first dielectric insulative layer 26 a tantalum nitride (TaN) layer
of about 2000 angstroms in thickness. It should be noted that the
TaN layer may be formed by sputtering the tantalum nitride (TaN)
over the entire exposed surfaces of the fifth wiring layer 27 and
first dielectric insulative layer 26, and then removing unnecessary
portions by dry etching. The TaN layer is formed over the
seat-electrodes 32a and 32b to form the resistor 32. The TaN layer
acts as a base membrane when forming a dielectric layer 19b of the
capacitor 19.
As shown in FIGS. 13 and 14, the capacitor 19 has the dielectric
layer 19b formed by baring the TaN layer formed on the
under-electrode 19a, forming, on the fifth wiring layer 27, an
anodization mask which covers other portions than the bared TaN
layer, applying a voltage to the TaN layer and anodizing the latter
to form a tantalum oxide (Ta.sub.2O.sub.5) layer. The anodization
mask is formed from a photoresist or silicon oxide easy to pattern,
for example, to have a thickness of several to several dozen
micrometers. This thickness assures a sufficient insulation of
other portions from the applied voltage. The TaN layer is anodized
in an electrolytic solution of ammonium borate, for example,
applied with a voltage of 50 to 200 V to be an anode. Thus the TaN
layer is oxidized at selected portions thereof to form a
Ta.sub.2O.sub.5 layer (dielectric layer 19b). In the step of
forming the element forming layer 3, the dielectric layer 19b of
the capacitor 19 and register 32 can be formed at the same time
through the aforementioned steps.
In the step of forming the element forming layer 3, an
upper-electrode 19c is formed on the dielectric layer 19b of the
capacitor 19 as shown in FIG. 14. The upper-electrode 19c is formed
on the fifth wiring layer 27 by sputtering Ni/Cu or Ti/Cu over the
fifth wiring layer 27 except for the dielectric layer 19b, for
example. The upper-electrode 19c thus formed has a predetermined
thickness and is opposite to the lower-electrode 19a with the
dielectric layer 19b laid between them as shown in FIG. 8.
Note that the TaN layer may wholly be anodized without use of any
anodization mask and then the resultant Ta.sub.2O.sub.5 layer be
appropriately patterned. Since the TaN layer of the resistor 32 is
also anodized at the surface thereof, the oxide layer will act as a
protective layer to maintain a stable performance of the inner TaN
layer.
In the step of forming the element forming layer 3, the second
dielectric insulative layer 28 is formed with the thin film
technology to fully cover the fifth wiring layer 27 after forming
the latter through the aforementioned steps, as shown in FIG. 15.
Also the second dielectric insulative layer 28 is formed from an
organic material excellent in high-frequency performance, thermal
resistance and chemical resistance by an appropriate thin film
technology capable of forming a layer having a uniform thickness,
such as spin coating or the like similarly to the aforementioned
first dielectric insulative layer 26. The second dielectric
insulative layer 28 is subjected to photolithography, exposure and
development, for example, to have formed therethrough viaholes 31
through which there will be exposed appropriate portions of the
fifth wiring layer 27 and upper-electrode 19c of the capacitor 19
as shown in FIG. 15.
The second dielectric insulative layer 28 has the sixth wiring
layer 29 with the inductor 20 formed on the surface thereof through
the similar forming steps to those through which the fifth wiring
layer 27 has been formed as shown in FIG. 16. The sixth wiring
layer 29 is formed through a step in which a thin metal layer of
Ni/Cu or Ti/Cu is formed by sputtering or the like on the inner
wall of the viahole 31 and over the second dielectric insulative
layer 28, a step in which the thin metal layer is subjected to
photolithography using a mask having a desired shape, and a step in
which the thin metal layer is etched to remove unnecessary thin
metal film with a wiring pattern being left.
The sixth wiring layer 29 has the aforementioned inductor 20 formed
thereon and is formed larger in thickness than the fifth wiring
layer 27 in order to improve the skin effect of the inductor 20.
Therefore, in the step of forming the sixth wiring layer 29, the
inductor 20 having a predetermined thickness as shown in FIG. 16
with the so-called semi-additive technique in which a Cu layer is
formed on a selected portion of the thin metal layer corresponding
to the inductor 20 by an electrolytic plating using copper, for
example, and then the solder resist is removed, the Ni/Cu layer is
wholly etched back by sputtering. The sixth wiring layer 29 is
formed thick at a predetermined portion of the wiring pattern
corresponding to the land 5, in addition to the inductor 20 formed
thereon by the aforementioned electrolytic plating of copper. It
should be noted that the inductor 20 is a spiral-shaped one in this
embodiment but it may of course be an appropriately-shaped one.
As shown in FIG. 17, the elements block 3 has formed thereon
opposite to the pattern openings 21 and 22 formed in the first
wiring layer 14 that acts as the ground of the base substrate block
2 the passive elements such as the capacitor 19 and inductor 20
formed through the aforementioned steps. Therefore, the passive
elements in the elements block 3 will not have the self-resonant
frequency thereof deteriorated by a capacitance developed between
them and the ground pattern and the performances thereof
deteriorated due to a reduction of the quality factor Q.
The sixth wiring layer 29 is covered with the insulative protective
layer 7 as shown in FIG. 17. The insulative protective layer 7 is
formed over the sixth wiring layer 29 by spin coating of a solder
resist or interlayer insulative material, for example. The
insulative protective layer 7 is subjected to photolithography
using a mask having a desired shape to have an opening formed
therethrough in a place corresponding to each land 5. In the step
of forming the elements block 3, the latter is formed to have
electrodes by making electroless Ni/Au or Ni/Cu plating, for
example, of the lands 5. The element forming layer 3 has the IC
chip 6 mounted thereon by flip-chip bonding with the lands 5 laid
between them, and has the insulative resin layer 8 formed thereon
to cover the IC chip 6, whereby the high-frequency module 1 shown
in FIG. 7 is formed.
Note that in the step of forming the high-frequency module 1
according to the present invention, a shielding cover is attached
on the elements block 3 to eliminate the effects of an
electromagnetic noise. Since a large heat from the IC chip 6 and
the like will possibly degrade the performance of the elements
block 3 in this case, the high-frequency module 1 may be designed
to appropriately dissipate the heat. For this purpose, a resin
material excellent in thermal conduction, for example, is provided
on the IC chip 6 to dissipate heat from the IC chip 6 at the
shielding cover via the resin material or a cooling viahole is
formed to provide a communication between the elements block 3 and
base substrate block 2 to dissipate such heat at the base substrate
block 2.
Also, since in the step of forming the high-frequency module 1, the
base substrate block 2 is formed from the organic substrate as a
core substrate with the so-called printed-circuit board technique
as mentioned above, the high-frequency module 1 can be produced
with a reduced costs. Also, since in the step of forming the
high-frequency module 1, the elements block 3 is stacked on the
flat buildup surface of the base substrate block, the passive
elements such as the capacitor 19, inductor 20, etc. can be formed
with an improved precision.
Also, since in the step of forming the high-frequency module 1, the
base substrate block 2 is formed from the first organic substrate
11, second organic substrate 12 or prepreg 13 using no woven glass
fabric as the core material as mentioned above, there can be
reduced the high-frequency module 1 in which the dielectric
property of the base substrate block 2 can be kept low and the
influence of woven glass substrate on the resonator pattern 23
formed as an inner layer is reduced. Also in the step of forming
the high-frequency module 1, since the aforementioned base
substrate block 2 is included, there can be formed in the elements
block 3 the passive elements such as the capacitor 19, inductor 20,
etc. whose performance is stable without being affected by the
woven glass fabric.
Therefore, the step of forming the high-frequency module 1 assures
the high-frequency module 1 which can be produced with an improved
yield and such a precision that no post-processing such as
adjustment is required. The high-frequency modules 1 thus produced
are uniform in quality.
In the aforementioned high-frequency module 1, the base substrate
block 2 is formed from the first organic substrate 11, second
organic substrate 12 or prepreg 13 using no woven glass fabric as
the core material. Since the high-frequency module 1 is
multilayer-structured and has the IC chip 6 etc. mounted thereon,
it has a practically sufficient mechanical strength, but this
mechanical strength is somewhat smaller than the conventional
multilayer substrate using the woven glass fabric. In the
high-frequency module 1 according to the present invention, in case
a woven glass fabric is used in the base substrate block 2, it will
only affect a portion of the element forming layer 3 where the
passive elements are formed.
The second embodiment of the high-frequency module according to the
present invention will be described below with reference to FIG.
18. This high-frequency module is generally indicated with a
reference 40. As shown in FIG. 18, the high-frequency module 40 has
the base substrate block 2 in which a second organic substrate 41
using a woven glass fabric 42 as a core material is used in place
of the aforementioned second organic substrate 12 as the lower
layer.
Note that since the high-frequency module 40 shown in FIG. 18 is
constructed of the same or similar components as or to those in the
aforementioned high-frequency module 1 except for the second
organic substrate 41, the components will be indicated with the
same or similar references as or to those for the components in the
high-frequency module 1 and will not be described in detail any
more.
In the high-frequency module 40 in FIG. 18, the second organic
substrate 41 formed from a both-side copper clad substrate is an
integration of an organic material whose specific inductive
capacity and loss are low with the woven glass fabric 42 as a core
material. The second organic substrate 41 is formed by continuously
supplying the woven glass fabric 42, formed by weaving glass fibers
into a mesh and rolled in the form of a roll, into a bath filled
with an emulsified organic material, thus saturating the woven
glass fabric with the organic material, adjusting the thickness of
the organic material-saturated woven glass fabric, drying the woven
glass fiber, and make some other processing of the woven glass
fabric to a desired thickness. Then, the second organic substrate
41 is formed by applying an adhesive to the top or bottom main side
of the substrate material as a core, bonding a rolled copper foil
having the surface thereof roughened to the substrate material and
cutting the latter to a predetermined size.
The second organic substrate 41 has the third and fourth wiring
layers 16 and 17 formed by photolithography and etching of each of
the top and bottom copper foil layers, and has also through-holes
in appropriate places. Since on the second organic substrate 41,
the third wiring layer 16 retains the copper foil layer as a ground
layer thereover as previously described, the woven glass fabric 42
as the core material is electrically isolated from the resonator
pattern 23 formed in the second wiring layer 15 and passive
elements formed in the elements block 3 not to directly affect the
resonator pattern 23 and passive elements.
The high-frequency module 40 shown in FIG. 18 has electrical
properties equal to those of the aforementioned high-frequency
module 1 according to the first embodiment of the present invention
and also is designed to have an improved mechanical strength. The
first organic substrate 11 and elements block 3 in the
high-frequency module 40 in FIG. 18 can be formed from an organic
material such as an acrylate resin, epoxy resin or polyolefin resin
which will still remain relatively soft even after having been
cured, for example. That is, the material for the first organic
substrate 11 and elements block 3 can be selected with a higher
freedom.
The third embodiment of the high-frequency module according to the
present invention will be described below with reference to FIG.
19. This high-frequency module is generally indicated with a
reference 50 in FIG. 19. The high-frequency module 50 is formed by
integrating first and second organic substrates 51 and 52 with a
prepreg 53 laid between them, and stacking a third organic
substrate 54 integrally on the first organic substrate 51 by
build-up or one-operation pressing. The high-frequency module 50
uses a both-side copper clad substrate as the first organic
substrate 51, having copper foil layers bonded to top and bottom
main sides, respectively, thereof and which form first and second
wiring layers 55 and 56, respectively, and also a both-side copper
clad substrate as the second organic substrate 52, having copper
foil layers bonded to top and bottom main sides, respectively,
thereof and which form third and fourth wiring layers 57 and 58,
respectively. Also, the high-frequency module 50 uses a one-side
copper clad substrate as the third organic substrate 54, having a
copper foil layer bonded to one main side thereof and which forms a
fifth wiring layer 59 that is the uppermost layer in the
high-frequency module 50.
In the high-frequency module 50 shown in FIG. 19, the second and
third organic substrates 52 and 54 include woven glass fabrics 60
and 61 as core material integrated thereto, respectively. Also in
the high-frequency module 50, the first organic substrate 51 and
prepreg 53 include no woven glass fabric. In the high-frequency
module 50, the first to third organic substrates 51, 52 and 54 are
stacked integrally on each other with a predetermined wiring
pattern being formed in each of the copper foil layers in the first
to third organic substrates 51, 52 and 54. The high-frequency
module 50 has a plurality of through-holes 62 formed through the
organic substrates stacked integrally on each other.
The first wiring layer 55 forms a ground layer with the copper foil
being left over the first organic layer 51. The second wiring layer
56 is formed by photolithography and etching of the copper foil
layer under the first organic substrate 51. The second wiring layer
56 forms a wiring for the control system, for example, and is
enclosed by the first and third wiring layers 55 and 57 as the
upper and lower ground layers to provide internal strip-line
structure lines. These strip-line structure lines form a resonator,
filter or coupler.
The third wiring layer 57 forms a ground layer with the copper foil
layer being left over the second organic substrate 52. The fourth
wiring layer 58 is formed by photolithography and etching of the
copper foil layer under the second organic substrate 52. The fourth
wiring layer 58 forms a wiring for the control system, for example,
and has multiple electrodes 25 formed thereon as in the
aforementioned high-frequency module 1. The high-frequency module
50 is thus mounted on an interposer (not shown). In the
high-frequency module 50 shown in FIG. 19, the fifth wiring layer
59 is formed by photolithography and etching of the copper foil
layer on the third organic substrate 54 stacked on the first
organic substrate 51. In the high-frequency module 50, multiple
lands 5 are formed on the fifth wiring layer 59, and the IC chip 6,
chips (not shown), etc. are mounted on the fifth wiring layer with
the lands 5 laid between them. It should be noted that the fifth
wiring layer 59 is covered with the insulative protective layer 7
for the purpose of protection.
To have an improved mechanical strength, the uppermost and lower
most layers of the high-frequency module 50 shown in FIG. 19 are
formed from the second and third organic substrates 52 and 54,
respectively, including the woven glass fabrics 60 and 61 as the
core materials, respectively, as mentioned above. In the
high-frequency module 50, the elements such as the resonator,
filter or coupler formed from the strip-line structure line are
formed on the second wiring layer 56 as an inner layer laid between
the first and third wiring layers 55 and 57 as the ground layers,
respectively, and thus the elements are electrically isolated from
the woven glass fabric. Therefore, in the high-frequency module 50,
the elements are kept stable in performance without being affected
by the woven glass fabrics 60 and 61 in the second and third
organic substrates 52 and 54.
Note that the structure of the high-frequency module 50 in FIG. 19
is not limited to the aforementioned one but multiple organic
substrates are stacked integrally on one each other. In the
high-frequency module 50, the passive elements such as the
capacitor, inductor, etc. may be formed, with the thin film
technology, in the wiring layers formed in a multilayer structure.
In this high-frequency module 50, the massive elements are formed
on an organic substrate including no woven glass fabric and which
is enclosed by the ground layers similarly to the aforementioned
strip-line structure line.
In the foregoing, the present invention has been described in
detail concerning certain preferred embodiments thereof as examples
with reference to the accompanying drawings. However, it should be
understood by those ordinarily skilled in the art that the present
invention is not limited to the embodiments but can be modified in
various manners, constructed alternatively or embodied in various
other forms without departing from the scope and spirit thereof as
set forth and defined in the appended claims.
INDUSTRIAL APPLICABILITY
In the high-frequency modules according to the present invention,
conductive parts are formed where no woven glass fabric is provided
so that the conductor parts will not be influenced by the woven
glass fabric and can thus have stable and improved performance
characteristic. Also according to the present invention, the
high-frequency modules are formed from relatively low-cost organic
substrates, which leads to a reduction of manufacturing cost. Since
the elements block is formed on the flat buildup surface of the
base substrate block, the conductive parts of the passive elements,
distributed parameter elements, etc. can be formed with a high
precision.
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